1. Field of the Invention
This invention relates in general to gas furnaces and, in particular, to the control of condensate within and transitting the collector box in a gas furnace. More specifically, but without restriction to the particular embodiment hereinafter shown and described, this invention relates to features which serve to drain condensate from the collector box, inhibit condensate blockage of pressure taps in the collector box, and reduce the condensate based blockage of condensing heat exchanger outlets into the collecting box.
2. Discussion of the Background Art
Gas furnaces typically include a primary heat exchanger positioned adjacent a burner box containing burners. During operation of the furnace, a blower moves circulating air over the heat exchanger to produce heated air that is then directed to a desired location. Gas is supplied to the burner box by a gas manifold having orifices that direct the gas into the burners. The gas exiting the burners is ignited by an ignitor provided in the burner box. The burners allow combustion of the gas and also direct heated flue gas into the heat exchanger. The typical heat exchanger includes cells with a channel or pass formed in each cell to direct the flow of flue gas produced by combustion. These cells are positioned side by side in a parallel manner and are provided with a predetermined spacing to allow the blower air to flow around the cells. The blower air is thus heated by convection as it circulates over the cells.
A sheet metal panel or cell panel having burner target plates is typically provided to position the burner box relative to the inlet side of the cells contained in the heat exchanger. An inducer having a motor and fan is typically mounted on the discharge side of the heat exchanger. The inducer is activated to induce a flow of flue gas through the heat exchanger and into vent piping so that the flue gas may be vented to a location exterior to the furnace.
A recent advance in the residential heating industry has been the development of condensing gas furnaces. These furnaces typically included a primary heat exchanger as well as a condensing heat exchanger. A blower, in this type of condensing furnace, provides circulating air flow over both heat exchangers to produce heated air that may be directed to a desired location by a system of ducts and registers.
In such condensing furnaces, both the primary heat exchanger and the condensing heat exchanger include cells with a channel or pass formed therein to direct the flow of flue gas produced by combustion. These cells in both the primary and secondary heat exchangers are positioned side by side in a parallel manner and are provided with a predetermined spacing to allow blower air to flow around both groups of heat exchanger cells. Gas is provided to the condensing furnace by a gas manifold having orifices that direct the gas into burners. The burner box is secured to the inlet side of the primary heat exchanger to align the discharge end of the burners with the inlet ports of the primary heat exchanger cells. The gas is ignited by an ignitor as it exits the burners contained in the burner box. The heated flue gas produced by combustion is then directed into the primary heat exchanger cells.
The condensing heat exchanger of the furnace is configured in a manner similar to that of the primary heat exchanger. A series of side by side condensing cells is provided, each of which has an inlet port for receiving flue gas discharged from the primary heat exchanger. The inlet ports of the condensing heat exchanger cells are aligned and secured in a sheet metal panel forming the inlet side of the condensing heat exchanger. The inlet side of the condensing heat exchanger is fluidly connected to the discharge side of the primary heat exchanger by a coupling box. The condensing cells function to exchange heat with the clean circulation air and to condense water vapor out of the products of combustion contained in the flue gas. This condensate drains from the condensing cells into a collector box provided on the discharge side of the condensing heat exchanger. The collector box extends through the cell panel below the burner box and includes tubing to further drain the condensate from the box into drain piping. The collector box is provided with an opening to which the intake side of an inducer is fluidly secured. The inducer in the condensing furnace induces the flow of heated flue gas through the cells in both the primary and condensing heat exchangers.
The collector box also contains a pressure tap located therein which serves to detect negative pressure which indicates normal inducer motor operation or excess fluid collecting in the box during abnormal furnace operation. This condition, which is intended to indicate a blocked drain or other problem, will result in furnace shutdown. If condensate blocks the opening to the pressure tap, the system may respond as if excess fluid is collecting. This is an undesirable result as it can lead to excess furnace cycling or even total shutdown necessitating a service call.
With recent advancements in the art, a commercially feasible condensing gas furnace having four possible installation orientations has been proposed by the assignee of the present invention. Such gas-fired furnaces are known in the art as multi-poise condensing furnaces and are disclosed, for example, in the copending, commonly assigned U.S. patent application Ser. No. 08/089697, entitled "Multi-Poised Condensing Furnace", and in U. S. Pat. No. 5,309,890to Rieke et al., U. S. Pat. No. 5,331,944 to Kujawa et al., U. S. Pat. No. 5,341,795 to Chou et al., U.S. Pat. No. 5,320,087 to Froman, U.S. Pat. No. 5,346,002 to Swilik, Jr. et al., U.S. Pat. No. 5,346,001 to Rieke et al., and U.S. Pat. No. 5,345,924 to Rieke et al. all assigned to the present assignee. The teachings of U.S. patent application Ser. No. 08/089697, and U. S. Pat. Nos. 5,309,890, 5,331,944, 5,341,795, 5,320,087, 5,346,002, 5,346,001, and 5,345,924 are all incorporated by reference as to their teachings of the construction and function of a multi-poise furnace.
These multi-poise furnaces are installable so that the circulating air that is being heated moves through the furnace in either an upflow, downflow, horizontal-right flow, or horizontal-left flow direction. The multi-positional properties of these furnaces results in a requirement for design features which will allow the furnace to function properly and just as efficiently in any one of these four possible installation orientations. In the prior art, for example, the pressure tap inside the collector box was protected from condensate by mitering the tap at about 45.degree. so that the upper portion overhung the lower. This device cannot be used in a multi-poise furnace as it would not be effective in different orientations.